FIG. 10 shows a system based on the conventional technology disclosed in a U.S. Pat. No. 4,430,864, which is comprised by: process air passage A; regeneration air passage B; two desiccant beds 103A, 103B; a heat pump 200 for regeneration of desiccant and cooling of process air. The heat pump 200 uses heat exchangers 220, 210 embedded in the desiccant beds 103A, 103B as high and low temperature heat sources respectively, in which one desiccant bed performs dehumidifying by passing process air, and the other desiccant bed performs regeneration of desiccant beds by passing regeneration air. After air conditioning is carried out for a specific time interval, four-way switching valves 105, 106 are operated to perform reverse processes in respective desiccant beds by flowing regeneration air and process air in the opposite desiccant beds.
In the conventional technology described above, high/low heat source of the heat pump 200 and each desiccant are integrated in each unit, and, an amount of heat equivalent to the cooling effect .DELTA.Q, is totally loaded on the heat pump (vapor compression cycle). That is, cooling effect cannot exceed the capability of the heat pump (vapor compression cycle) used. Therefore, there is no benefit resulting from making the system complex.
Therefore, to resolve such problems, it is possible to consider a system, such as the one shown in FIG. 11, to heat the regeneration air by placing a high temperature source 220 in the regeneration air passage B, and placing a low temperature air source 240 in the process air passage A to cool the process air, as well as to provide a heat exchanger 104 for exchanging sensible heat between the post-desiccant process air and pre-desiccant regeneration air. In this case, the desiccant 103 uses a desiccant wheel which rotates so as to straddle the process air passage A and the regeneration air passage B.
This system can provide cooling effects (.DELTA.Q), which is a sum of the cooling effects produced by the heat pump and the cooling effects produced by sensible heat exchange performed between process air and regeneration air, as shown in the psychrometric chart presented in FIG. 12, thus producing a system of more compact design and capable of generating a higher cooling effects than that produced by the system shown in FIG. 10.
However, even in this type of air conditioning system, when processing a relatively low sensible heat load, as may happen during the rainy season, producing a relatively low temperature and a high humidity, it is difficult to obtain a heat balance between the heat produced by the heat pump needed for desiccant regeneration and the cooling load for sensible heat processing, resulting that, if priority is given to obtain dehumidification, the temperature of the conditioning space may become too low because cooling of supply air in the low-temperature heat source heat exchanger 240 can cause excessive cooling.
This invention has been made to solve the problems outlined above by providing an air conditioning system that can produce continual dehumidification of supply air and desiccant regeneration, by developing a system that enables to adjust the heat transfer process in the sensible heat exchanger disposed between the post-desiccant process air that has not yet flowed into the low-temperature heat source heat exchanger and regeneration air that has not yet flowed into the high-temperature heat source heat exchanger. When air conditioning is aimed primarily at dehumidification of process air with a low sensible heat fraction, heat transfer processes in the sensible heat exchanger are controlled so as to retain the sensible heat load in the low-temperature heat source heat exchanger, thereby increasing the temperature of supply air into the conditioning space. Such a system, when operated according to the method presented, conserves energy while exhibiting superior dehumidifying capability and flexibility in processing a variety of cooling loads.